Barras texturadas de (Bi_1.6Pb_0.4)Sr₂CaCu₂O_8+δ dopadas con Ag

Abstract

In this work, superconducting samples of (Bi 1.6 Pb 0.4 )Sr 2 CaCu 2 O 8+δ with Ag additions have been studied. (Bi 1.6 Pb 0.4 )Sr 2 CaCu 2 O 8+δ + x wt.% Ag (with x = 0, 1 and 3) powders were synthesized using a sol-gel method. The obtained powders were used as precursors to fabricate long textured cylindrical bars through a floating zone melting method. A drastic change on the microstructure has been found when comparing with undoped Bi 2 Sr 2 CaCu 2 O 8+δ samples. The results showed that electrical resistivity at room temperature, critical current as well as flexural strength are improved when Ag is added to these Pb doped samples, while critical temperature does not change. On the other hand, it has been found that samples with composition (Bi 1.6 Pb 0.4 )Sr 2 CaCu 2 O 8+δ + Ag shown E-I curves with very high sharpness values on the zone of the superconducting to normal transition, reaching n-values (E∼I n ) as high as 45 at 65K. Keywords: Superconductors, electrical properties, mechanical properties, Bi-2212, melting zone Barras texturadas de (Bi 1.6 Pb 0.4 )Sr 2 CaCu 2 O 8+δ dopadas con AgSe han preparado polvos cerámicos de composición (Bi 1.6 Pb 0.4 )Sr 2 CaCu 2 O 8+δ + x % Ag en peso (con x = 0, 1 y 3) mediante un proceso sol-gel. Estos polvos se han utilizado para fabricar precursores que se texturaron por medio del método de fusión zonal flotante. Se ha encontrado un gran cambio en la microestructura cuando se compara con muestras de composición pura Bi 2 Sr 2 CaCu 2 O 8+δ . Tanto la resistividad eléctrica a temperatura ambiente, como la corriente crítica, así como la resistencia a flexión se mejoran cuando la Ag se adiciona a estas muestras dopadas con Pb, mientras que no se observa cambio en la temperatura crítica. Por otra parte, se ha encontrado que las muestras de composición (Bi 1.6 Pb 0.4 )Sr 2 CaCu 2 O 8+δ + Ag presentan una gran pendiente de la curva E-I en la zona de transición entre el estado superconductor y el estado normal. Con estas composiciones, se han encontrado valores de n (E∼I n ) de hasta 45 a 65K.

Effect of Yb-substitution on thermally activated flux creep in the Bi2Sr2Ca1Cu2−xYbxOy superconductors

“…Other techniques used to improve the transport properties are based on the grain orientation [36,37]. Among all these techniques, the Laser Floating Zone Melting (LFZ) technique has been shown as a very reliable process to obtain well-aligned Bi-2212 grains, with their c-axis nearly perpendicular to the growth direction, and very small amounts of secondary phases [38][39][40][41][42][43].…”

Growth Speed and Substitution Effects on Alignment and Thermal Transport Properties of Bi-2212 Textured Superconductors

“…Lasers are widely used in fabrication of BSCCO rods and coatings while the halogen lamps are mostly preferred in fabrication of BSCCO single crystals in infrared radiation furnaces [6,7]. The main advantage of using laser as heat source in melt processing is the possibility of obtaining very high thermal gradients at the solidification interface, compared to resistive and other type of heaters [8][9][10][11][12][13]. High temperature gradient is a strong requirement to fabricate materials having highly aligned grains in a comparatively fast manner.…”